Systemic lupus erythematosus (SLE) is a chronic systemic disease characterized by episodic, unpredictable exacerbations and by remissions, usually associated with treatment. The clinical challenge is to reliably assess increasing disease activity, so that treatment can prevent permanent organ damage and premature death. Several reliable clinical activity indices exist. However, no single laboratory parameter to date has proven sufficiently reliable and valid to predict disease activity in SLE. Since SLE is an antigen driven autoimmune disease, we hypothesize that serologic tests can be predictors of flares in the next month. Furthermore, we hypothesize that a weighted combination of serologic tests will be a stronger predictor of clinical lupus flares than the individual scrologic tests. We propose a longitudinal clinical study of 50 SLE patients who will be followed monthly for 12 months. Our aim is to determine and validate prospectively which serologic tests (anti-double-stranded DNA antibodies by Crithidia vs. ELISA or Farr assays, standard complement levels vs. complement split-products) are predictors of clinical lupus flare using regression models. The results of this study will have immediate clinical utility: if we find positive predictors, the tests will become standard in SLE monitoring; if there are no serologic predictors, these tests will not be ordered and health care savings will result.